The subject matter disclosed herein relates generally to systems and methods for diagnostic medical imaging, and more particularly to Molecular Breast Imaging (MBI) systems.
Molecular Breast Imaging (MBI) is used to image breasts to detect, for example, tumors, lesions, and/or cancer. In operation, a patient is positioned within the MBI system such that the patient's breast is positioned between a pair of detectors. A plurality of two-dimensional (2D) images of the patient's breast is then acquired. More specifically, the detectors include a plurality of pixels that generate counts that are proportional to the energy spectrum of the radiopharmaceutical radiating from the patient.
In operation, the patient is injected with a radiopharmaceutical such as, for example, Technetium-99 (Tc99). As the radiopharmaceutical decays, the emitted gamma rays have a predefined energy spectrum that is typically unique for the radiopharmaceutical being utilized. For example, Tc99 has an energy spectrum having a peak energy of approximately 140 keV. The gamma rays are then detected by the detectors as counts which are subsequently used to generate an image of the patient. To identify the counts, the detectors utilize a predefined acceptance window such that gamma rays within a predetermined energy range of the radiopharmaceutical being imaged are defined as counts.
However, when the detectors are fabricated using a Cadmium Zinc Telluride, (CZT) material, the energy spectrum of the gamma rays includes a tail, e.g. additional information that is acquired outside of the energy window. For at least one known CZT detector, the total counts within the predefined acceptance window may therefore be composed of only approximately 60% of the energy spectrum of the Tc99. Accordingly, for CZT detectors, the conventional energy window may not be appropriately sized to include all the useful information or counts in the energy spectrum. As a result, because the count rate for each pixel in the detector is utilized to determine an intensity value for each pixel in the final image, various features of interest in the generated image may be difficult to distinguish from background tissue in the image.